Recently, technique for suppressing release of carbon dioxide into the atmosphere has been developed as global warming and air pollution becomes more severe. Particularly, a method of efficiently trapping carbon dioxide emitted from thermoelectric power plants or boiler equipment has been increasingly developed.
Among various methods of trapping gas, it is widely known that chemical absorption method using absorbent liquid is most suitable for trapping carbon dioxide of large capacity. According to a gas collecting plant using the chemical absorption method, carbon dioxide emitted from thermoelectric power plants or boiler equipment is absorbed in absorbent liquid in an absorption tower and saturated absorbent liquid containing carbon dioxide is heated in a regeneration tower so as to separate regeneration gas containing the carbon dioxide from the absorbent liquid.
According to a conventional gas collecting plant, the carbon dioxide and the absorbent liquid are contacted with each other at a rectifier mounted in the absorption tower. At this time, an apparatus for collecting the absorbent liquid at a center portion of the rectifier is mounted in a filler or a separating plate for separating gas evenly is mounted in an upper portion of the absorption tower so as to prevent channeling occurring when the absorbent liquid passes through the filler in the rectifier. That is, channeling of gas and liquid is prevented by changing a structure of an upper portion of the absorption tower. However, it is very difficult to control abnormal phenomena due to fast linear velocity of gas at a lower portion of the absorption tower and absorbent liquid drop.
In addition, a reboiler for heating the absorbent liquid is mounted at the regeneration tower as energy source for regeneration. The reboiler heats the absorbent liquid up to a temperature at which the regeneration is possible so as to separate the gas contained in the absorbent liquid. The gas separated from the absorbent liquid moves to an upper portion of the regeneration tower such that useful material is collected into a condenser and the gas that is removing object is discharged from the regeneration tower.
Conventionally, a reboiler of kettle type or a reboiler of thermocyphon type is used.
The reboiler of kettle type includes first and second parts therein divided by a wall. A heater or a heat-exchanger is disposed in the first part and an absorbent liquid outlet is formed at the second part. If the absorbent liquid containing the gas is supplied to an upper portion of the reboiler, a level of the absorbent liquid in the reboiler rises. At this time, the absorbent liquid is heated by the heater or the heat-exchanger and the gas is separated from the absorbent liquid and moves upwardly. As the absorbent liquid is supplied continuously, the absorbent liquid from which the gas is removed or which contains less gas crosses the wall and moves to the second part. After that, the absorbent liquid is discharged from the reboiler through the absorbent liquid outlet. According to the reboiler of kettle type, slosh occurs due to liquid wave generated by liquid drop and boiling of mixed liquid. Therefore, it is very difficult to control a level of the absorbent liquid precisely.
The reboiler of thermocyphon type includes a heater or a heat-exchanger therein and an absorbent liquid outlet is formed at a bottom surface of the reboiler. If the absorbent liquid containing the gas is supplied to an upper portion of the reboiler, the absorbent liquid in the reboiler is heated by the heater or the heat-exchanger and the gas is separated from the absorbent liquid and moves upwardly. At this time, the absorbent liquid from which the gas is removed or which contains less gas moves toward the bottom surface of the reboiler and is discharged from the reboiler through the absorbent liquid outlet. According to the reboiler of thermocyphon type, a level of the absorbent liquid is hard to be controlled due to boiling. In addition, since there is no wall in the boiler, the mixed liquid remains in the reboiler in a very short time. Therefore, less energy is supplied to the mixed liquid and gas separation efficiency for regeneration is very low.
In addition, a supply path of the mixed liquid and a discharge path of the gas separated from the mixed liquid are same in the reboiler of kettle type and the reboiler of thermocyphon type. Therefore, if bubbles occur due to heating, the mixed liquid cannot reach the heater or the heat-exchanger by the bubbles. If this condition continues, the level of the mixed liquid in the regeneration tower is so raised too high that the absorption tower and the regeneration tower cannot work.
Furthermore, a gas collecting plant using the chemical absorption method includes a condenser for condensing the regeneration gas and generating condensate, and a reflux apparatus for discharging gas evaporated from the condensate to an exterior thereof to collect the gas and supplying the condensate back into the regeneration tower.
According to a conventional gas collecting plant, the condenser and the reflux apparatus are separately disposed in order to control a level of the condensate in the reflux apparatus. As a result, a volume of the gas collecting plant becomes large and a large space is necessary to mount the gas collecting plant. In addition, since the reflux apparatus and the condenser are separated, a large amount of heat loss occurs between the reflux apparatus and the condenser.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.